Process for polymerizing vinyl compounds containing a basic nitrogen atom



PROCESS FOR POLYMERIZING VINYL COM- Kg glISIDS-CONTAINING A BASIC NITROGEN John A. Price, Stamford, and Walter M. Thomas, Noroton Heights, Conn., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application May 20, 1955 Serial No. 510,043

11' Claims. or. 260-805) The present invention relates to a process for improving the yield in flue polymerization and copolymerization of basic monomers containing an unsaturated group.

An, object of the invention is to provide an im method for vinyl polymerization.

Another object of the invention-is to provide an improved process for the catalytic'polymerization of material containing a basic monomer having an unsaturated group.

A further object of the invention is to provide an improved catalytic process for copolymerizing mixtures of basic vinyl monomers with acrylic compounds'in which a higher conversion is obtained. I

Other objects and advantages of the invention will be apparent to those skilled in the art, especially upon consideration of the detailed disclosure hereinbelow.

It has been found that the conversion efficiency or yields obtained in polymerizing basic monomers containing an unsaturated group with a chlorate ion-sulfoxy' ion catalyst system is surprisingly increased in the presenceofnitrate roved include monomeric compounds containing an ethylenic group and a basic nitrogen atom; for example, primary,

secondary and tertiary amines of the aliphatic, cycle- During polymerization in an aqueous system containing a chlorate-sulfoxy catalyst combination, the chlorine is re? duced and the sulfur simultaneously oxidized.

To obtain optimum results, it is recommended that the oxidizing and reducing components be present in oxidationand reduction equivalents; that is, 3 mols of sulfurous acid, or a sulfite per mol of chlor'ic acid or a chlorate. The ratiois the same for bisulfites, but only- 1.5' mols of a metabisulfite salt is required since such salts ionize to form H80 ions. By reason of having double the reduction potential of sulfites, only 1.5 mols of a thiosulfate' or a salt of hydrosulfurous acid (H S O is required per mol of chlorate to accomplish the same results. It should be understood that these proportions are not critcial and that it is possible to depart greatly from the ideal ratio, as for example by using equimolar amounts of sodium bi-1 sulfite and sodium chlorate or in charging 6 mols of the bisulfite, per mol of the chlorate with no otherdisadvan tage than a trivial waste of catalytic material. In general, it is recommended that the amount of chlorate ions introduced should be between about 0.01 and about 1.0% of the weight of the polymerizable monomeric material and that the sulfoxy ions be present in a quantity ranging between about 0.01 and about 3.0% by weight on the same basis. Larger amounts of the catalyst components, such as 3 or more percent of chlorate ions and 9 or-more percent of sulfoxy ions, are operative; but they produce no additional benefits. When the polymerization medium-- contains nitrate ions, a distinct improvement in conversion" is obtained in polymerizing monomers containing a C=C group and a basic nitrogen atom and in copolymerizing one or more of such monomers with one or aliphatic, aromatic or heterocyclic type, as well as similar quaternary ammonium compounds.

The invention, accordingly, comprises polymerizing a compound containing both a C=C group and a basic nitrogen atom alone or with one or more basic or non basic monomers containing a similar unsaturatedjgroup in an acidic aqueous medium comprising nitrate ions, chlorate ions, and oxidizablesulfoxy ions of'the' group consisting of sulfite, bisulfite, hydrosulfite and thiosulfate ions. Narrower aspects of the invention relate to the ployed with much success in the polymerization of various f vinyl compounds, including vinyl chloride, acrylonitrile, vinyl acetate, etc. They have been found to be particularly suitable for the homoandcopolymerization of acrylonitrile into polymers of excellent characteristics for the manufacture of synthetic fibers. While the components of an oxidation-reduction or redox catalyst system of this nature may be introduced as chloric and sulfurous acid, these acids are relatively unstable; therefore, itfis usually more convenient to add the desired ions tothe polymerization system in" the form of a water-soluble chlorate salt and a water-soluble sulfite salt, together with a suitable acid such'as sulfuric acid, phosphoric acid, or acetic acid. For

selected. a 1

economy, sulfuric acid ,is usually more other unsaturated compounds. Strangely enough, no appreciable improvement is produced by the nitrate ions in the polymerization of vinyl compounds of a nonbasic nature in theabsence of the aforesaid basic monomers. The reason for these effects is not com-" pletelyunderstood. The present process is applicable to the polymerization of basic monomers alone or in thepresence of other comonomers capable of addition polymerization/ The unsaturated basic compound may constitute an extremely," small amount of the total polymerizable matter present, as for instance as little as 0.5%, and still display a noticeable improvement in'yield when polymerized in the presence of nitrate ions. 'In addition to'a basic nitrogen atom,

' these basic monomers must contain one or more un-' 60 proportions of various components of the catalyst, the

saturated double bonds; and this unsaturation may be '1' either conjugated or unconjugated. The present process is particularly applicable to materials containing a singleterminal ethylenic group; and these comprise the most significant materials which'are subjected' to vinyl or addition polymerization in commerce today. Moreover,

outstanding results are obtained in the present'pro'cess' with compounds of this type. With the use'of suitable pressure equipment, the new process can be employed with gaseous'monom'ers, as Well as those which are liquids ethyl fumarate, and N-3-cyclohexylaminopropyl acry l-.-

amide.

The processof the present invention is not only applil cable'to thev homo'polyrnerization of the above basic or? ganic compounds but also to the copolymerization of two'-" or more of them and alsoto the copplymerizationof one, or more of the basic monomers with one or more nonbasic compounds of the type described immediately below.

awhile: the. polymerization process described herein. is

applicable to the product; of. copolymers of. acrylonitrile in, major proportions-,-. as "for instance, 50?.

to..95%; by weight,-; withg a. 'minorproportion rof a basic monomer, aster instanceto. 15% by weight with. or. without, other.. copolymerizable substances; itfis by: now mcaps limited? to thesei materials. on proportions; They are'gmerely polymers which have proven especially suit:

ahleofor spinning into synthetic fibers having an excellent poundsph commercefall into this .classr, .The suitable I comouomersinclude; inter alia, allyl alcohol, ethylene,

styrene; the mono-a and ;di}nuclear substituted; methyl-., ethyl-; chloro nitrorstyrenes, acryliccompounds general;1 ly,.i. e. acrylic acid,;methacrylic acid, the alkyl, aryl, and. aralkylesters of acrylic and methacrylic acids, the corre-' sponding. amides and mono-N-alkyl, derivatives, thereof;- methacrylonitrile, etc; unsaturated ketones such as methyl: vinyl ketone, miscellaneous vinyl compounds such as vinyl chloride, .vinyl acetate; vinylchloracetate, vinyl butyrate, vinylstearate,.. etc., butadiene,-.. vinylidene: chloride, acrolein,;diallyl phthalate, vinyl ethylether, variousethyl-q en ically unsaturated .fluorineecontaining compounds .jasexemplified by trifluorochloroethylene, diethyl; fumarate,xdimethylrnaleateand the like.

To.achieve the benefits of this invention, .itisessential. thatnitrate ions bepresentwin the polymerization medium alongg with thechlorate and sulfoxy ions; Nitric acid. maybe ,used. for thepurposeo'r any ofits, inorganic salts since all such nitrates are water-soluble. ,Inasmuchas a PHbtYJen1 and 5 isnecessary in the polymerizationrreaction, and nitric acidhassatisfactory stability in storage; 1 the rsimplest and easiest way of cha'rgingthe nitratejaions'r is inthe form of nitric acid which also serves to adjust the pH tothe proper value; This avoids introducing anyi:

' foreigmsubstances, such as the 'sulfatepions' in. sulfuric acid, ,whichhaveino efiectzin promoting or catalyzing the reaction. In'general the quantity.ofnitrate-cions may ranzfi from about 0.5 toabout.80.%;ofithe totalweight'of polymerizable matter in. the system; and quantities" ranging tronraboutl to about:1:20%vare preferred; The

necessary quantity of nitrate ions may beexprelssedainranotherway; that is, asequiv'alent toat leastthe amount of i nitric acid. required. to produce "a pH of from about 1 to TSin, a: polymerization system containing the basic monomer; Sodium or potassiumjchlorateland sodium=or potassium :bisulfite oranother of the designatedsulfoxy salts. This quantitywill, of"course, vary somewhat at anyselected pH depending on the basicity oftheparticular unsaturated basic. monomer. Additionalrnitrate.ions

fecting the pH by adding the nitrate salt of sodium,potassium, calcium, magnesium, aluminum, etc.&

.Polymerizations. may be carriedout in aqueous soluQ i polymer before spinning. Howevenwith waterinsolublc monomers in. other. applications of this; process,

"iilli k r who sat -i a ent should be selected. Such, surface active agents may be of the anionic type, as exemplified by sulfonated paraffin oil, alkylated naphthalene sulfonates, sodium lignosulfonate, the salts of long chain alkyl sulfates and sulfonates like sodium cetylsulfate and sodium lauryl sulfate, and the sodium, potassium, and amine soaps of long chain (12 to 22.;carbon atoms) fatty acids. Cationic emulsifiers may alsorbe. used; ,as'for instance, cetyl trimethyl ammonium I chloride etc, to the reaction mixture.

bythisv or anyother means, thepolymer is readily filtered may be introduced where r desirable.withoutmaterially afthe resulting polymer 1 suspension has excellent pumping characteristics, well Tasoutstanding drainage or filtering qualities. inprocessing. and handling. a smaller volume of the 'reaction mixture. No difliculties are encounteredin respect to. separation .of theqmonomer since the polymcrizable matterv is-chargjedv at a rate correlated with the rate of.

polymerization in such;.a manner thatthe system is never saturated with monomeric acrylonitrile.

.In the continuous polymerization of. monomers containing a major proportion of acrylonitrile, the optimum pH has been found to ,be between about 1.8 and about 2.5, whereas the optimum for batch operations ranges from about 2.8-;tol about 3.5.

.Relatively low polymerization temperatures, for'examplethoserangingfromabout 20C. toabout 70 C., aredesirable;anditemperatures of. about 30 to about 50 C. are particularly recommended.

It? is desirable to, conduct" the process of the present invention .in. the absence: of oxygen: which has a definite it inhibiting-j efiect on. the polymerization. Suitable inert gases :such as mitrogenand carbon dioxide may be :used to I displace air in the reactionzone.

In-som'e'cases; the polymer or copolymer formedwill.

precipitate out of solution substantially completely; in other cases, it may be desirable to add a precipitating .or coagulating electrolyte such as sodium chloride, sodium sulfate, aluminum sulfate, hydrochloric acid, calcium fromtheliquid medium, washed and dried.

Fillers,.- dyes, pigments, plasticizers, other resins ,.'both' natural. and synthetic, and. the like may be:incorporated p with the polymers and copolymers eitherxbefore, during% or; after." polymerization to .render'the productsv more suitable ,forwhateveruse they are to be put, i. e., moldinggand surface coa-tingcompositions, adhesives, fibers,

For the preparation of acrylonitrile polymers-or co polymers-tabs used in: the preparation of spun fibers, a

uniform .molecularweightlof between about 60,000 and about. 9 0; 000 hasj been found to be most desirable. It

is saniadvantage of the new process thatby continuous. addition.- of the catalyst system a uniform average pressed-ton simplicity as anhydrous or HNO, and. Ha o4,..even.thoughaqueousnitric and sulfuric acids.

are actuallynemployed, In-order to provide faircom-T parisonsmfi the ,effects:produced.by the introduction.of.- the nitrate ions, it has been necessary to employ relatives- Additional economies are, of course, realized.

When coagulated For example, the acid 1y few monomer and comonomer compositions with limited variation of the catalyst concentrations andother reaction conditions. Accordingly, the examples are not to be interpreted as attempting to s'etforth any ranges of reaction conditions or of suitable monomers.

EXAMPLE I A reaction vessel, equipped with a stirrer, reflux condenser, thermometer and gas inlet tube, is placed in a constant temperature bath which is maintained at 40 C. To the vessel is added a solution of 95.4 vparts of acrylonitrile, 5.3 parts of 2-methyl-5-vinyl pyridine, 5.3 parts of vinyl acetate, 950 parts of demineralized water and 2.76 parts by weight of HNO The pH of the initial solution is 3.2. A rapid stream ofpre-purified nitrogen is passed over the surface of the solution for 30 minutes, and then is reduced to 2 or 4 bubbles per second. A solution of 0.440 part of sodium chlorate and 1.575 parts of sodium sulfite in 100 parts of water is made up. A second solution is prepared by adding 1.17 parts of HNO to 100 parts of water. Portions of these solutions are added at 25-minute intervals to the reaction vessel over a period of 2 /2 hours. The polymerization is continued for a total period of four hours. At the end of this time the product is collected on a Biichner funnel, and it is washed with 2000 parts of demineralized water. The polymer is dried in an oven at 70 C. for about 16 hours. The yield of dry white polymer of acrylonitrile, 2-methyl-5-vinyl pyridine and vinyl acetate amounts to 77 parts which represents a 73% conversion. 7

Comparative Example A The same conditions and quantities are used as in Example I, except that the 2.76 parts of HNO used in the initial charge is replaced with 2.175 parts of H 80 and the pH of the mixture is 3.2. Also, the 1.17 parts of HNO in the acid feed is replaced with 091 part. of H 80 In this case, the yield of dry, white tripolymer of acrylonitrile, 2-methyl-5-vinyl pyridine, and vinyl acetate amounts to 70 parts which represents a 66% conversion or a relative yield of about 10%" less than with nitric acid.

Comparative Example B Example I is repeated in all respects except for a different monomer charge which consists of 100.7 parts of acrylonitrile and 5.3 parts of methyl acrylate with no basic comonomer present. The pH of the reaction mixture is between 2.9 and 3.2. The yield of dry white copolymer of acrylonitrile" and methyl acrylate amounts to 92 parts which is equivalent to an 87% conversion.

Comparative Example C Example B is duplicated exactly except for the substitution of 2.175 parts of H 80, for the nitric acid in the initial charge and 0.91 part of H 80 for the nitric acid in the catalyst solution. Again, a yield of 92 parts of acrylonitrile-methyl acrylate copolymer is obtainedwhich indicates that the improvement obtained with nitric acid is specific to recipes containing basic monomers.

EXAMPLE H Comparative Example D This example illustrates the preparation of a ternary polymer from a mixture of 90% acrylonitrile, 5% 2, methy1-5-vinyl pyridine, and 5% vinyl acetate by'weight reaction is stopped at the end of 5 hours.

The copolymerizationdsetfected continuously, using apparatus which includes amnion vessel provided with an overflow tube located at the top. Agitation is'3efiected primarily by circulating the contents of the reaction vessel continuously through a high-speed centrifugal pump. Additional stirring in the reaction vessel is effected by means of a motor-driven propeller The temperature is regulated by means ofa heat exchanger located in the external circulating. system. The solutions of monomeric material and of acid and catalyst hereafter described are fed into the reaction vessel using variable-speed pumps. 1

The reactor is charged with a previously prepared 28% aqueous slurry of a two-component copolymer of about acrylonitrile and 5% methyl acrylate. The following solutions are then fed in simultaneously at the indicated rates.

The temperature of the slurry is maintained at 40 C.,

and the average pH is about 2.2. The residence or aver:

age. holding time .is 2 hours, and the copolymerization The ternary polymer isisolated from the final reactor slurry by centrifuging;- then it is washed in the centrifuge with 40,000 parts of demineralized water and dried in an oven at 70 C. for about 16' hours. The weight of dry, white ternary polymer of acrylonitrile, 2-methyl-5 -vinyl pyridine, and vinyl acetate amounts to 1100 parts which represents a 64% conversion.

, EXAMPLE lII Example D is repeated using the following feeds which differ chiefly in the substitution of nitricacid for sulfuric acid. The same equipment is employed, and the product slurry left in the reactor from Example D serves to seed the present reaction.

Again the temperature of the slurry is maintained at 40 C., and the average pH is 2.2. At the end of 5 hours, the reactor slurry is isolated, washed and dried in the same manner as described in the preceding example. The small amount of iron present as ferrous sulfate is helpful in maintaining a fluid slurry which can be pumped despite its high concentration ofsolids. The yield of dry, white ternary polymer of acrylonitrile, 2-methyl-5-vinyl pyridine, and vinyl acetate amounts to 1340; parts which represents a 78% conversion, a relative improvement of 22% over the yield in Example D.

i re wy-q; The term polymer of D- .is. prepared in exactly; thetsame mannerwusing the followingr feeds:

The overall pH of the reaction is substantially 2.1. The yield of dry white ternary polymer of acrylonitrile, Z-methyl-S-vinyl pyridine andviny-P acetate amounts to 1460 parts which represents aconversion; of 85%;

EXAMPLE v Exactly the same. procedure is-followed as described in Example. IV with theexeeption. that 18.4 parts of sodiumunitrate is also added-to Feed 3. The yield of dry white polymer of acrylonitrile, 2-methyl-5-vinyl pyridine and vinyl acetate amounts to 1560 parts which represents a91% conversion.

' EXAMPLE VI This'examplel illustrates the preparation of. a' ternary polymer containingv'by weight a'bout 885% acrylonitrile,

6.5% Z-methyl-S-vinylpyridine,and 5.0% vinyl acetate" units following th'eprocedure of ExampleD in general.

Partsper hour Feed 1:

Sodium chlorate 7.3 Sodium sulfite s 26.0 40 Demineralized' water 1030.0

Feed 2:

Acrylonitrile 850.0 Vinyl acetate 75.0 475" Feed 3: 1 y2-methyl-5-vinyl pyridine 75.0 HNO v 48.5 Ferrous sulfate 0.0256 The. temperature of the slurry is maintained at 50 C.

After 6 hours of running, equilibrium conditions are established with the pH at. about 2.0. andthe slurry is collected at Z-hour intervals for the next-18:.hours. The polymer from each "Eaten dentin; is isolated; .Washed and dried in the same manner as before. The average conversion for the l8-hour period amounts to 84%.

5'60 'I'lletemperature of the slurry is maintained at 5 0 C. and the pH again is about 2.0. After 6 hours of running, equilibrium conditions are established, and the slurry is collected, washed and dried at 2f-hour intervals for the next 18 hours. The average conversion for the 18-hour period amounts to 94% EXAMPLE VIII To a reaction vesselv equipped'as in Example I are added 46.8 parts of N-3-dimethylaminopropyl acrylamide, 950 parts of demineralized water and 19 parts of HNO The pH of the initial solution is about 3.0.. A rapid stream of pre-purified nitrogen is passed over the surface of the solution for 30 minutes. and is then reduced to 2 or 4 bubbles. per second. A solution of 0.880 part of sodium chlorate. and 3.15 parts of sodium sulfite in 100 parts of water is made up; A second solution is prepared by adding 2.40 parts'of HNO to 100 parts of water. Portions of these solutions are added at 25-minute intervals to the reaction vessel over a period of 2 /2 hours. The polymerization is continued for a total period of four hours at 40 C. .At the end of this time, the viscosityof the solution is substantially greater than at the start indicating that most of theN-Bdimethylaminopropyl 'acrylamide'nitrate has polymerized to a water-soluble polymer.

While there areabove disclosedbut a limited number of embodiments of the process herein presented, it is possible I to produce still other embodiments without departing from the" inventive concept herein disclosed.

What we claim is: 1. A process which comprises polymerizing a compound containing both a O=C group and a basic nitrogen atom selectedfrom the group consisting of vinyl.

pyridines, alkyl vinyl pyridines,.quaternary ammonium derivatives of said pyridines, monoand di-allylamine, lower alkyl mono-, and di-allylamines, aminoalkyl acrylates and aminoalkyl acrylamides an aqueous solution of pH between about 1 and about 5 comprising nitrate ions, chlorate ions, and oxidizable sulfoxy ions of the group consisting of sulfite, bisulfite, and hydrosulfite and thiosulfate ions; i

2. A process according to claim 1 in which said compound is copolymerizedwith' a comonomer containing a' C=C group and free of; basic nitrogen atoms. 3. Aprocess accordingto claim 1 in which said compound is copolymerized with acrylonitrile.

4. A process which comprises polymerizing a compound containing both a C=C group and a basic nitrogen atom selected from the group consisting of vinyl pyridines, alkyl vinyl pyridines, quaternary ammonium derivatives of said pyridines, monoand di-allylamine, lower alkyl monoand di-allylamines, aminoalkyl acrylates and aminoalkyl acrylamides in-an aqueous solution of pH between about 1 and about 5 comprising at least about 0.5 percent nitrate ions, at least about 0.01 percent chlorate ions, and at least about 0.01percent oxidizable sulfoxy ions of the group consisting of sulfite; bisulfite', hydrosulfite and thiosulfate ions based upon the weight of polymerizable material. j Y 1 5. A process according to claim 4 in which said compound is copolymerized'with a comonomer containing a C=C group and free of basic nitrogen atoms.

6. A process according to'clairn 4 in which said compoundis copolymerized with acrylonitrile.

' 7. A process which comprises polymerizing a compound containing both a'CI-IFC group and a basic nitrogen atom selected from the group consisting of vinyl pyridines, alkyl vinyl pyridines, quaternary ammonium I derivatives of said pyridines; monoand di-allylamine,

lower alkyl monoand di-allylamines, aminoalkyl acrylates and aminoalkyl acrylamides at a temperature between about20 andabout7O degrees centigrade in an aqueous solution'of pH between about 1 and about 5 5 comprising between about 0.5' and about 80- percent nitrate ions, between about 0.01 and about 3 percent chlorate ions; and between about 0.01 and about 9 percent oxidizable sulfoxy ions of the group consisting of sulfite, bisulfite, hydrosulfite and thiosulfate ions based upon the weight of polymerizable material.

8. A process according to claim 7 in which said compound is copolymerized with a co-monomer containing a CH =C group and free of basic nitrogen atoms.

9. A process according to claim 7 in which said compound is copolymerized with acrylonitn'le.

10. A process which comprises polymerizing a major proportion of acrylonitrile and a minor proportion of a vinyl pyridine at a temperature between about 20 and about 70 degrees centigrade in an aqueous solution comprising between about 0.01 and about 1.0 percent of 15 chlorate ions from an alkali metal chlorate, between 10 I about 0.01 and about 3.0 percent of sulfoxy ions from an alkali metal salt of sulfurous acid based upon the weight of polymeriza'ble material and sufiicient nitric acid to produce a pH between about 1 and about 5 in the solution.

11. A process according to claim 10 in which the polymerizable material charged comprises about 80 to about 90 percent by weight of acrylonitrile, about 5 to about 10 percent Z-methyl-S-vinyl pyridine and about 5 to 10 10 percent vinyl acetate.

Hill Mar. 23, 1954 

10. A PROCESS WHICH COMPRISES POLYMERIZING A MAJOR PROPORTION OF ACRYLONITRILE AND A MINOR PROPORTION OF A VINYL PYRIDINE AT A TEMPERATURE BETWEEN ABOUT 20 AND ABOUT 70 DEGREES CENTIGRADE IN AN AQUEOUS SOLUTION COMPRISING BETWEEN ABOUT 0.01 AND ABOUT 1.0 PERCENT OF CHLORATE IONS FROM AN ALKALI METAL CHLORATE, BETWEEN ABOUT 0.01 AND ABOUT 3.0 PERCENT OF SULFOXY IONS FROM AN ALKALI METAL SALT OF SULFUROUS ACID BASED UPON THE WEIGHT OF POLYMERIZABLE MATERIAL AND SUFFICIENT NITRIC ACID TO PRODUCE A PH BETWEEN ABOUT 1 AND ABOUT 5 IN THE SOLUTION.
 11. A PROCESS ACCORDING TO CLAIM 10 IN WHICH THE POLYMERIZABLE MATERIAL CHARGED COMPRISES ABOUT 80 TO ABOUT 90 PERCENT BY WEIGHT OF ACRYLONITRILE, ABOUT 5 TO ABOUT 10 PERCENT 2-METHYL-5-VINYL PYRIDINE AND ABOUT 5 TO 10 PERCENT VINYL ACETATE. 